Near field measurements of bistatic scattering from random rough surfaces

Efficient and accurate measurement of bistatic scattering patterns of point and distributed targets using a near-field measurement system is demonstrated. A planar (3 m/spl times/3 m) near-field scanning system is designed and constructed which makes use of an HP 8720D network analyzer as its transmitter, receiver, and signal processing units. The near-field probe of this system is dual polarized to facilitate polarimetric bistatic scattering measurements. Issues such as calibration procedure for removing systematic errors such as channel imbalances, probe cross-talk, and characterization of radiometric calibration constants are discussed. Also measurement procedures for isolating and removing the transmitter leakage as well as the algorithm for near-field to far-field transformation are described. Finally measured bistatic scattering of point targets with known RCS patterns are compared with their theoretical values and very good agreement is obtained.